• Title/Summary/Keyword: low frequency

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The Effect of Sling Exercise Therapy with Vibration Balls on Upper Limb Muscle Activity for Paraplegia-Spinal Cord Injury

  • Oh, Ju Hwan;Kwon, Tae Kyu
    • Korean Journal of Applied Biomechanics
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    • v.28 no.3
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    • pp.187-191
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    • 2018
  • Objective: The purpose of the present study is to investigate the effect of a muscle activity by applying the complex exercise method of sling in accordance with the provision of various vibration intensities for paraplegia-spinal cord injury. Method: The subjects of the study were 15 men in their 40s and 50s with lower limb disabilities and low potential risk, who were randomly divided into a sling exercise group (SG n=4), a sling with low frequency vibration group (SLVG n=4), a sling with mid-frequency vibration group (SMVG n=4), and a sling with high frequency group (SHVG n=4) in accordance with the provision of slings and vibration stimuli. The vibratory intensity provided was divided into low frequency (30 Hz), mid-frequency (50 Hz), and high frequency (70 Hz). The anterior deltoid (AD), the posterior deltoid (PD), the pectoralis major (PM), the upper trapezius (UT), the latissimus dorsi (LD), and the multifidus (MF) were measured to compare and analyze muscle activity. Results: The closed kinetic chain (CKC) exercise to the shoulder joint showed higher muscle activity in most muscles for the SMVG, and statistically significant differences in the anterior deltoid (AD), the pectoralis major (PM), and the multifidus (MF) in particular. Conclusion: The intermediate frequency (50 Hz) string vibration was the effective vibration stimuli for Closed kinetic chain (CKC) exercises.

ER-Fuzz : Conditional Code Removed Fuzzing

  • Song, Xiaobin;Wu, Zehui;Cao, Yan;Wei, Qiang
    • KSII Transactions on Internet and Information Systems (TIIS)
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    • v.13 no.7
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    • pp.3511-3532
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    • 2019
  • Coverage-guided fuzzing is an efficient solution that has been widely used in software testing. By guiding fuzzers through the coverage information, seeds that generate new paths will be retained to continually increase the coverage. However, we observed that most samples follow the same few high-frequency paths. The seeds that exercise a high-frequency path are saved for the subsequent mutation process until the user terminates the test process, which directly affects the efficiency with which the low-frequency paths are tested. In this paper, we propose a fuzzing solution, ER-Fuzz, that truncates the recording of a high-frequency path to influence coverage. It utilizes a deep learning-based classifier to locate the high and low-frequency path transfer points; then, it instruments at the transfer position to promote the probability low-frequency transfer paths while eliminating subsequent variations of the high-frequency path seeds. We implemented a prototype of ER-Fuzz based on the popular fuzzer AFL and evaluated it on several applications. The experimental results show that ER-Fuzz improves the coverage of the original AFL method to different degrees. In terms of the number of crash discoveries, in the best case, ER-Fuzz found 115% more unique crashes than did AFL. In total, seven new bugs were found and new CVEs were assigned.

Clinical Observation on Delivery of Low Birth Weight Unfant (저출생 체중아 분마에 대한 임상적 고찰)

  • Song, Seon-Ho;Choi, Euy-Soon
    • Women's Health Nursing
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    • v.5 no.2
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    • pp.191-203
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    • 1999
  • A clinical study was made on 365 low birth weight infant and 406 normal birth weight infant who had been born at Kangnam St. mary's Hospital during past 3 years from Jan. 1, 1995 to Dec. 31, 1997. the data of this study were gathered through reviewing of medical records. 1. Comparison of general characteristic with of obstetric characteristic 1) Old maternal age, previous abortion and previous LBWI delivery in the group of low birth weight infant(LBWI) mother were more prevalent than those in the group of normal birth weight infant(NBWI)mother 2) Cesarean section, abnormal presentation and multiple pregnancy in the group of LBWI mother were prevalent than those in the group of NBWI mother. 3) regular antenartal care and visiting rate of tertiary hospital in the group of LBWI mother were more prevalent than those in the group of NBWI mother. 2. Frequency of low birth weight infant 1) Anmual average frequency of LBWI was 6.5% and monthly frequency was the highest in January and december. 2) The frequency of LBWI was the highest in 37-40wks of gestational age and was the highest in 2251-2500 gm of birth weight. 3) The frequency of congenital anomaly in the group of LBWI was more prevalent than that of NBWI. 3. Mortality rate of LBWI The mortality rate of LBWI was 9.2%. The highest mortality rate was noted before 27wks of gestational age, less than 1000gm of birth weight and within 12hrs of delivery. 4. The most common complication of pregnant women was pre-term labor, the most complication relating to placenta was premature rupture of membrane(PROM) and the most fetal complication was fetal distress in delivered LBWI. 5. Significant relating factors of low birth weight infant delivery were associated with maternal age, previous delivery, previous low birth weight delivery, pre-eclampsia, anemia, oligohydramnios, PROM, placenta previa, abruptio placenta, fetal sex, fetal distress and congenital anomaly.

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A study on bulk deposition flux of dustfall and insoluble components by the wind intensity in Busan, Korea (바람의 강도에 따른 강하먼지와 불용성 성분의 조성특성)

  • 황용식;김유근;박종길;문덕환
    • Journal of Environmental Science International
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    • v.11 no.7
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    • pp.651-662
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    • 2002
  • Weather elements were observed by the AWS (Automatic Weather System) and dustfall particles were collected by the modified American dust jar (wide inlet bottle type) at 4 sampling sites in Busan area from March. 1999 to February, 2000. Thirteen chemical species (Al, Ca, Cd, Cr, Cu, Fe, K, Mg, Mn, Ni, Pb, Si, and Zn) were analyzed by AAS and ICP. The purposes of this study were to estimate qualitatively various bulk deposition flux of dustfall and insoluble components by applying regional and seasonal wind intensity. Frequency of wind speed were found in order of low(1-3m/s), very low(<1m/s), medium(3-8m/s) and high(>8m/s), and annual mean had higher range at low(1-3m/s) for 56.3%. Strong negative linear correlation were observed between dustfall and wind direction (northeastern and eastern), but strong positive linear correlation were observed between dustfall and wind direction (western and northwestern) at industrial, commercial and coastal zone(p<0.05). While a negative correlation were observed between wind speed frequency of very low(<1 m/s) and dustfall, and positive correlation were observed between wind speed frequency of low(1-3m/s) and dustfall in coastal zone(p<0.05). The correlation coefficient was observed 0.556 between wind speed frequency of low(1-3m/s) and Ni by commercial zone(p<0.05). The correlation coeffcient show well-defined insoluble trace metals (Al, Ca, Cr, Cu, Fe, Pb, and Zn) and wind speed frequency of low(1-3m/s) at coastal zone, which was found significant difference(p<0.01).

Fuel Droplet Entrainment and Low Frequency Instability in Hybrid Rocket Combustion (하이브리드 로켓 연소에서 연료액적의 발생과 저주파수 연소불안정)

  • Kim, Jina;Lee, Changjin
    • Journal of the Korean Society for Aeronautical & Space Sciences
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    • v.49 no.7
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    • pp.573-580
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    • 2021
  • Paraffin wax is attracting many attentions for promising solid fuel of hybrid rocket because of its higher regression than other fuels. However, even with paraffin fuel combustion, unsteady low-frequency oscillation of combustion pressure is still observed. And, this is related to the formation of liquid layer and the entrainment of fuel droplets entering the axial combustion gas flow. This study investigates the effect of additional combustion of fuel droplets on the occurrence of low-frequency combustion instability. On the other hand, the formation of fuel droplets depends on Weber Number (the ratio of the inertial force to the surface tension of the liquid) and Reynolds Number of the oxidizer flow. Therefore, a laboratory-scale hybrid rocket was used to monitor the occurrence of combustion instability while changing We number. A series of combustion tests were conducted to control We number by changing the oxidizer flow rate or adding LDPE (low density polyethylene) to base fuel. In the results, it was confirmed that there is a critical We number above which the low-frequency combustion instability occurs.

Frequency Effects of Upstream Wake and Blade Interaction on the Unsteady Boundary Layer Flow

  • Kang, Dong-Jin;Bae, Sang-Su
    • Journal of Mechanical Science and Technology
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    • v.16 no.10
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    • pp.1303-1313
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    • 2002
  • Effects of the reduced frequency of upstream wake on downstream unsteady boundary layer flow were simulated by using a Wavier-Stokes code. The Wavier-Stokes code is based on an unstructured finite volume method and uses a low Reynolds number turbulence model to close the momentum equations. The geometry used in this paper is the MIT flapping foil experimental set-up and the reduced frequency of the upstream wake is varied in the range of 0.91 to 10.86 to study its effect on the unsteady boundary layer flow. Numerical solutions show that they can be divided into two categories. One is so called the low frequency solution, and behaves quite similar to a Stokes layer. Its characteristics is found to be quite similar to those due to either a temporal or spatial wave. The low frequency solutions are observed clearly when the reduced frequency is smaller than 3.26. The other one is the high frequency solution. It is observed for the reduced frequency larger than 7.24. It shows a sudden shift of the phase angle of the unsteady velocity around the edge of the boundary layer. The shift of phase angle is about 180 degree, and leads to separation of the boundary layer flow from corresponding outer flow. The high frequency solution shows the characteristics of a temporal wave whose wave length is half of the upstream frequency. This characteristics of the high frequency solution is found to be caused by the strong interaction between unsteady vortices. This strong interaction also leads to destroy of the upstream wake strips inside the viscous sublayer as well as the buffer layer.

Design of a 2.5GHz CMOS PLL Frequency Synthesizer Using a High-Speed Low-Power Prescaler (고속 저전력 프리스케일러를 사용한 2.5GHz CMOS PLL 주파수합성기 설계)

  • Kang, K.S.;Oh, G.C.;Lee, J.K.;Park, J.T.;Yu, C.G.
    • Proceedings of the IEEK Conference
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    • 2005.11a
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    • pp.877-880
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    • 2005
  • This paper describes a PLL frequency synthesizer for wireless LNA applications. The design is focused mainly on low-power and low-phase noise characteristics. A 128/129 dual-modulus prescaler has been designed using the proposed TSPC D flip-flops for high-speed operation and low-power consumption The designed synthesizer includes all building blocks for elimination of external components, other than the crystal. Its operating frequency can be programmed by external data. The frequency synthesizer has been designed using a $0.25{\mu}m$ CMOS process parameters. It operates in the frequency range of 2GHz to 3GHz and consumes 3.2mA at 2.5GHz from a 2.5V supply.

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Heavy-weight Impact Noise Reduction of Concrete Slab Reinforcement Using F.R.P (F.R.P 재료 보강에 의한 신개념 중량충격음 저감대책)

  • Jeong, Jeong-Ho;Yoo, Seung-Yup;Lee, Pyoung-Jik;Jeon, Jin-Yong;Jo, A-Hyoung
    • Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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    • 2005.05a
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    • pp.383-386
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    • 2005
  • Low frequency heavy-weight impact noise is the most irritating noise in Korean high-rise reinforced concrete apartment buildings. This low frequency noise is generated by foot traffic due to the fact that Koreans do not wear shoes at home. The transmission of the noise is facilitated by a load bearing wall structural system without beams and columns which is used in these buildings. In order to control low frequency heavy-weight impact noise, floating floors using isolation materials such as glass-wool mat and poly-urethane mat are used. However, it was difficult to control low frequency heavy-weight impact sound using isolation material. In this study, reinforcement of concrete slab using beams and plate was conducted. Using the FEM analysis, the effect of concrete slab reinforcement using FRP(fiber-glass reinforced plastic) on the bang machine impact vibration acceleration level and sound were conducted at the standard floor impact sound test building. The $3{\sim}4dB$ floor impact vibration acceleration level and impact sound pressure level were reduced and the natural frequency of slabs were changed.

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Vibration effects on remote sensing satellite images

  • Haghshenas, Javad
    • Advances in aircraft and spacecraft science
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    • v.4 no.5
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    • pp.543-553
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    • 2017
  • Vibration is a source of performance degradation in all optical imaging systems. Performance of high resolution remote sensing payloads is often limited due to satellite platform vibrations. Effects of Linear and high frequency sinusoidal vibrations on the system MTF are known exactly in closed form but the low frequency vibration effects is a random process and must be considered statistically. Usually the vibration MTF budget is defined based on the mission requirements and the overall MTF limitations. For analyzing low frequency effects, designer must know all the systems specifications and parameters. With a good understanding of harmful vibration frequencies and amplitudes in the system preliminary design phase, their effects could be removed totally or partially. This procedure is cost effective and let the designer to eliminate just harmful vibrations and avoids over-designing. In this paper we have analyzed the effects of low-frequency platform vibrations on the payload's modulation transfer function. We have used a statistical analysis to find the probability of imaging with a MTF equal or greater than a pre-defined budget for different missions. The worst and average cases have been discussed and finally we have proposed "look-up figures". Using these look-up figures, designer can choose the electro-optical parameters in such a way that vibration effects be less than its pre-defined budget. Furthermore, using the results, we can propose a damping profile based on which vibration frequencies and amplitudes must be eliminated to stabilize the payload system.

Effect of Bias Magnetic Field on Magnetoelectric Characteristics in Magnetostrictive/Piezoelectric Laminate Composites

  • Chen, Lei;Luo, Yulin
    • Journal of Magnetics
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    • v.20 no.4
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    • pp.347-352
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    • 2015
  • The magnetoelectric (ME) characteristics for Terfenol-D/PZT laminate composite dependence on bias magnetic field is investigated. At low frequency, ME response is determined by the piezomagnetic coefficient $d_{33,m}$ and the elastic compliance $s_{33}^H$ of magnetostrictive material, $d_{33,m}$ and $s_{33}^H$ for Terfenol-D are inherently nonlinear and dependent on $H_{dc}$, leading to the influence of $H_{dc}$ on low-frequency ME voltage coefficient. At resonance, the mechanical quality factor $Q_m$ dependences on $H_{dc}$ results in the differences between the low-frequency and resonant ME voltage coefficient with $H_{dc}$. In terms of ${\Delta}E$ effect, the resonant frequency shift is derived with respect to the bias magnetic field. Considering the nonlinear effect of magnetostrictive material and $Q_m$ dependence on $H_{dc}$c, it predicts the low-frequency and resonant ME voltage coefficients as a function of the dc bias magnetic field. A good agreement between the theoretical results and experimental data is obtained and it is found that ME characteristics dependence on $H_{dc}$ are mainly influenced by the nonlinear effect of magnetostrictive material.